Semiconductor device

ABSTRACT

A semiconductor device may include a first conductor plate, a first semiconductor element that is a sole semiconductor element disposed on a main surface of the first conductor plate, an encapsulant encapsulating the first semiconductor element and a first power terminal connected to the first conductor plate within the encapsulant and projecting from the encapsulant along a first direction. The main surface of the first conductor plate may include a first side located close to the first power terminal and a second side located opposite the first side with respect to the first direction. With respect to the first direction, a distance from the first semiconductor element to the first side may be larger than a distance from the first semiconductor element to the second side.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No.2018-174049, filed on Sep. 18, 2018, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The technology disclosed herein relates to a semiconductor device.

BACKGROUND

Japanese Patent Application Publication No. 2014-154779 describes asemiconductor device. This semiconductor device includes conductorplates, two semiconductor elements disposed on the conductor plates, andpower terminals extending from the conductor plates.

SUMMARY

In the above-described semiconductor device, the two semiconductorelements are disposed on their corresponding conductor plates in abalanced manner. As such, in conventional semiconductor devices, one ormore semiconductor elements are disposed on a conductor plate in abalanced manner. A semiconductor device where a sole semiconductorelement is present on a conductor plate, therefore, is usually designedsuch that the semiconductor element is located at a center of theconductor plate. However, the semiconductor device does not necessarilyhave a symmetric structure, and its power terminal, for example, isoften provided only on one side of the conductor plate. In this case,not disposing the semiconductor element simply at the center of theconductor plate, a positional relation between the semiconductor elementand the power terminal should be taken into account to dispose thesemiconductor element on the conductor plate. The disclosure hereinprovides a technology for this, which enables improvement in asemiconductor device.

A semiconductor device disclosed herein may comprise a first conductorplate, a first semiconductor element that is a sole semiconductorelement disposed on a main surface of the first conductor plate, anencapsulant encapsulating the first semiconductor element, and a firstpower terminal connected to the first conductor plate within theencapsulant and projecting from the encapsulant along a first direction.The main surface of the first conductor plate may comprise a first sidelocated close to the first power terminal and a second side locatedopposite the first side with respect to the first direction. Withrespect to the first direction, a distance from the first semiconductorelement to the first side may be larger than a distance from the firstsemiconductor element to the second side. It should be noted that “afirst semiconductor element that is a sole semiconductor elementdisposed on a main surface of the first conductor plate” means that onlya single semiconductor element is present on the first conductor plate,which is called a first semiconductor element herein.

In the above-described semiconductor device, the first power terminal isconnected to the first conductor plate. In such a configuration, heat ofthe first power terminal could transfer to the first semiconductorelement via the first conductor plate. For example, the first powerterminal may generate heat since the first power terminal allows arelatively large current to flow therein. Moreover, the first powerterminal is often welded to an external circuit member (e.g., a busbar), and tends to generate relatively large amount of heat at itswelded site. If such heat transfers to the first semiconductor element,a temperature of the first semiconductor element is thereby risen, whichmay, for example, create a need to restrict an operation of the firstsemiconductor element. In this regard, the structure of theabove-described semiconductor device allows the first semiconductorelement to be disposed not at a center of the first conductor plate, butat a position relatively apart from the first power terminal. Thissuppresses transfer of the heat of the first power terminal to the firstsemiconductor element via the first conductor plate.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a plan view of a semiconductor device 10 in an embodiment.

FIG. 2 shows an internal structure of the semiconductor device 10 in aplan view along a direction perpendicular to conductor plates 22, 24,26, 28.

FIG. 3 is a cross-sectional view along a line III-III in FIG. 1.

FIG. 4 shows a circuit structure of the semiconductor device 10.

FIG. 5 is a diagram for explaining an arrangement of a firstsemiconductor element 12 relative to the first conductor plate 22, andan arrangement of a second semiconductor element 14 relative to thethird conductor plate 26.

FIG. 6 is a diagram for explaining an arrangement of the firstsemiconductor element 12 relative to the second conductor plate 24, andan arrangement of the second semiconductor element 14 relative to thefourth conductor plate 28.

FIG. 7 is a diagram for explaining an arrangement of the firstsemiconductor element 12 and the second semiconductor element 14relative to a first connector portion 38, and an arrangement of thefirst semiconductor element 12 and the second semiconductor element 14relative to a second connector portion 40.

FIG. 8 is a diagram showing a process of molding an encapsulatingmaterial 50 a with use of a mold at a time point in the process.

FIG. 9 is a diagram showing the process of molding the encapsulatingmaterial 50 a with use of the mold at a time point later than the timepoint in FIG. 8.

DETAILED DESCRIPTION

In an embodiment of the present technology, the distance from the firstsemiconductor element to the first side may be equal to or larger than ahalf of a size of the first semiconductor element with respect to theabovementioned first direction (i.e., a direction in which the firstpower terminal projects). As such, the distance from the firstsemiconductor element to the first side (which is approximately adistance from the first semiconductor element to the first powerterminal) may be set sufficiently larger than that in conventionalsemiconductor devices. This can effectively suppress transfer of theheat of the first power terminal to the first semiconductor element viathe first conductor plate.

In an embodiment of the present technology, with respect to the firstdirection, the distance from the first semiconductor element to thefirst side may be at least twice the distance from the firstsemiconductor element to the second side. As such, the firstsemiconductor element may be disposed to be sufficiently offset relativeto the center of the first conductor plate. This can effectivelysuppress transfer of the heat of the first power terminal to the firstsemiconductor element via the first conductor plate.

In an embodiment of the present technology, the semiconductor device mayfurther comprise a second conductor plate opposed to the first conductorplate with the first semiconductor element interposed therebetween, andthe second conductor plate may comprise a main surface connected to thefirst semiconductor element within the encapsulant. However, if thesemiconductor device includes the second conductor plate, the heat ofthe first power terminal could transfer to the first semiconductorelement via the encapsulant and the second conductor plate. Therefore,in an embodiment, the main surface of the second conductor plate maycomprise a first side located close to the first power terminal and asecond side located opposite the first side with respect to the firstdirection. Then, with respect to the first direction, a distance fromthe first semiconductor element to the first side of the secondconductor plate may be larger than a distance from the firstsemiconductor element to the second side of the second conductor plate.Such a configuration can suppress transfer of the heat of the firstpower terminal to the first semiconductor element via the encapsulantand the second conductor plate (especially via the second conductorplate).

In an embodiment of the present technology, the semiconductor device mayfurther comprise a third conductor plate located side by side with thefirst conductor plate in a second direction perpendicular to the firstdirection, a second semiconductor element that is a sole semiconductorelement disposed on a main surface of the third conductor plate withinthe encapsulant, and a second power terminal connected to the thirdconductor plate within the encapsulant and projecting from theencapsulant along the first direction. However, in such a structure,heat of the second power terminal could transfer to the secondsemiconductor element via the third conductor plate. Therefore, in anembodiment, the main surface of the third conductor plate may comprise afirst side located close to the second power terminal and a second sidelocated opposite the first side with respect to the first direction.Then, with respect to the first direction, a distance from the secondsemiconductor element to the first side of the third conductor plate maybe larger than a distance from the second semiconductor element to thesecond side of the third conductor plate. Such a configuration cansuppress transfer of the heat of the second power terminal to the secondsemiconductor element via the third conductor plate. It should be notedthat “a second semiconductor element that is a sole semiconductorelement disposed on a main surface of the third conductor plate” meansthat only a single semiconductor element is present on the thirdconductor plate, which is called a second semiconductor element herein.

In an embodiment of the present technology, the third conductor platemay be connected to the second conductor plate via a first connectorportion located between the second conductor plate and the thirdconductor plate. In this case, in a plan view along a directionperpendicular to the third conductor plate, at least a half of the firstsemiconductor element and at least a half of the second semiconductorelement may be each located within a region defined by virtuallyexpanding the first connector portion in the second direction. Such aconfiguration allows the first connector portion to be disposedrelatively near the first semiconductor element and the secondsemiconductor element. This shortens a current path between the firstsemiconductor element and the first connector portion, and a currentpath between the second semiconductor element and the first connectorportion, thus electrical loss in these paths can be reduced.

In an embodiment of the present technology, the semiconductor device mayfurther comprise a fourth conductor plate opposed to the third conductorplate with the second semiconductor element interposed therebetween, anda third power terminal connected to the fourth conductor plate withinthe encapsulant and projecting from the encapsulant along the firstdirection. In this case, the fourth conductor plate may be located sideby side with the second conductor plate in the second direction and maybe connected to the third power terminal via a second connector portion.Then, in a plan view along a direction perpendicular to the fourthconductor plate, the second connector portion may be located between thesecond conductor plate and the fourth conductor plate and may be furtherlocated between the third power terminal and the first connectorportion.

In the above-described embodiment, in the plan view along the directionperpendicular to the fourth conductor plate, neither the firstsemiconductor element nor the second semiconductor element may belocated within a region defined by virtually expanding the secondconnector portion in the second direction, although not particularlylimited thereto. Such a configuration allows the first semiconductorelement and the second semiconductor element to be located apart fromthe second connector portion and the third power terminal, and hence cansuppress transfer of heat of the third power terminal to the firstsemiconductor element and the second semiconductor element.

Representative, non-limiting examples of the present disclosure will nowbe described in further detail with reference to the attached drawings.This detailed description is merely intended to teach a person of skillin the art further details for practicing aspects of the presentteachings and is not intended to limit the scope of the presentdisclosure. Furthermore, each of the additional features and teachingsdisclosed below may be utilized separately or in conjunction with otherfeatures and teachings to provide improved semiconductor devices, aswell as methods for using and manufacturing the same.

Moreover, combinations of features and steps disclosed in the followingdetailed description may not be necessary to practice the presentdisclosure in the broadest sense, and are instead taught merely toparticularly describe representative examples of the present disclosure.Furthermore, various features of the above-described and below-describedrepresentative examples, as well as the various independent anddependent claims, may be combined in ways that are not specifically andexplicitly enumerated in order to provide additional useful embodimentsof the present teachings.

All features disclosed in the description and/or the claims are intendedto be disclosed separately and independently from each other for thepurpose of original written disclosure, as well as for the purpose ofrestricting the claimed subject matter, independent of the compositionsof the features in the embodiments and/or the claims. In addition, allvalue ranges or indications of groups of entities are intended todisclose every possible intermediate value or intermediate entity forthe purpose of original written disclosure, as well as for the purposeof restricting the claimed subject matter.

EMBODIMENTS

With reference to the drawings, a semiconductor device 10 in anembodiment will be described. The semiconductor device 10 in the presentembodiment is a power semiconductor device, and can be used for a powerconversion circuit, such as a converter and an inverter, in anelectric-powered vehicle, such as an electric vehicle, a hybrid vehicle,and a fuel-cell vehicle. However, application of the semiconductordevice 10 is not limited particularly. The semiconductor device 10 canbe widely adopted for various devices and circuits.

As shown in FIGS. 1 to 4, the semiconductor device 10 includes a firstsemiconductor element 12, a second semiconductor element 14, and anencapsulant 50 encapsulating these semiconductor elements 12, 14. Theencapsulant 50 is constituted of an insulating material. The encapsulant50 in the present embodiment is formed by molding an encapsulatingmaterial (e.g., an epoxy resin) with use of a mold 100 (see FIGS. 8 and9), although not particularly limited thereto.

The two semiconductor elements 12, 14 are power semiconductor elements,and have configurations identical to each other. The first semiconductorelement 12 includes a lower electrode 12 a, an upper electrode 12 b, anda plurality of signal pads 12 c. The lower electrode 12 a is located ona lower surface of the first semiconductor element 12, and the upperelectrode 12 b and the plurality of signal pads 12 c are located on anupper surface of the first semiconductor element 12. Similarly, thesecond semiconductor element 14 includes a lower electrode 14 a, anupper electrode 14 b, and a plurality of signal pads 14 c.

As an example, the semiconductor elements 12, 14 are each a ReverseConducting (RC)-Insulated Gate Bipolar Transistor (IGBT) in which anIGBT and a diode are integrally provided in a single semiconductorsubstrate. Collectors of the IGBTs and cathodes of the diodes areconnected to the corresponding lower electrodes 12 a, 14 a, and emittersof the IGBTs and anodes of the diodes are connected to the correspondingupper electrodes 12 b, 14 b. The semiconductor elements 12, 14 are eachnot limited to an RC-IGBT, and may be a power semiconductor element ofanother type, simply such as an IGBT and a Metal-Oxide-SemiconductorField-Effect Transistor (MOSFET). Moreover, a material of theirsemiconductor substrates is not limited particularly, and may be, forexample, silicon (Si), silicon carbide (SiC), or a nitridesemiconductor.

The semiconductor device 10 further includes a first conductor plate 22,a second conductor plate 24, a third conductor plate 26, and a fourthconductor plate 28. The conductor plates 22, 24, 26, 28 are eachconstituted of a conductor such as copper or another metal. Theconductor plates 22, 24, 26, 28 may each be a laminated substrate (alsotermed an insulated substrate) that includes an insulator substrate anda conductor layer formed on the insulator substrate. The first conductorplate 22 and the second conductor plate 24 are opposed to each other,and the first semiconductor element 12 is interposed therebetween. Thelower electrode 12 a of the first semiconductor element 12 is solderedto a main surface 23 of the first conductor plate 22, and the upperelectrode 12 b of the first semiconductor element 12 is soldered to amain surface 25 of the second conductor plate 24 via a conductor spacer13. The main surface 23 of the first conductor plate 22 and the mainsurface 25 of the second conductor plate 24 are located within theencapsulant 50 and are opposed to each other.

Similarly, the third conductor plate 26 and the fourth conductor plate28 are opposed to each other, and the second semiconductor element 14 isinterposed therebetween. The lower electrode 14 a of the secondsemiconductor element 14 is soldered to a main surface 27 of the thirdconductor plate 26, and the upper electrode 14 b of the secondsemiconductor element 14 is soldered to a main surface 29 of the fourthconductor plate 28 via a conductor spacer 15. The main surface 27 of thethird conductor plate 26 and the main surface 29 of the fourth conductorplate 28 are located within the encapsulant 50 and are opposed to eachother.

The third conductor plate 26 is electrically connected to the secondconductor plate 24 at a first connector portion 38 located within theencapsulant 50. The first semiconductor element 12 and the secondsemiconductor element 14 are thereby electrically connected in series.As an example, the first connector portion 38 is located between thesecond conductor plate 24 and the third conductor plate 26, a part ofthe first connector portion 38 is integrally configured with the secondconductor plate 24, and another part thereof is integrally configuredwith the third conductor plate 26. As another embodiment, at least apart of the first connector portion 38 may be configured as a memberindependent of the second conductor plate 24 and the third conductorplate 26.

The first conductor plate 22 is exposed to outside at a lower surface ofthe encapsulant 50, and the second conductor plate 24 is exposed tooutside at an upper surface of the encapsulant 50. As such, the firstconductor plate 22 and the second conductor plate 24 configure part ofconductive paths in the semiconductor device 10 as well as function asheat-dissipating plates that dissipate heat of the first semiconductorelement 12 to outside. Similarly, the third conductor plate 26 isexposed to outside at the lower surface of the encapsulant 50, and thefourth conductor plate 28 is exposed to outside at the upper surface ofthe encapsulant 50. As such, the third conductor plate 26 and the fourthconductor plate 28 also configure part of conductive paths in thesemiconductor device 10 as well as function as heat-dissipating platesthat dissipate heat of the second semiconductor element 14 to outside.

The semiconductor device 10 further includes a first power terminal 32(a P terminal), a second power terminal 34 (an O terminal), and a thirdpower terminal 36 (an N terminal). The power terminals 32, 34, 36 eachextend across inside and outside the encapsulant 50. As an example, thethree power terminals 32, 34, 36 are parallel to one another and projectfrom the encapsulant 50 along a first direction (up-down direction inFIGS. 1 and 2). The first power terminal 32 is connected to the firstconductor plate 22 within the encapsulant 50. The second power terminal34 is connected to the third conductor plate 26 within the encapsulant50. The third power terminal 36 is connected to the fourth conductorplate 28 within the encapsulant 50.

In the present embodiment, the first power terminal 32 is configuredintegrally with the first conductor plate 22, and the second powerterminal 34 is configured integrally with the third conductor plate 26,although not particularly limited thereto. The third power terminal 36is connected to the fourth conductor plate 28 via a second connectorportion 40. As an example, the second connector portion 40 is locatedbetween the second conductor plate 24 and the fourth conductor plate 28,a part of the second connector portion 40 is configured integrally withthe fourth conductor plate 28, and another part thereof is configuredintegrally with the third power terminal 36. As another embodiment, atleast a part of the second connector portion 40 may be configured as amember independent of the fourth conductor plate 28 and the third powerterminal 36.

The semiconductor device 10 further includes a plurality of first signalterminals 42 and a plurality of second signal terminals 44. These signalterminals 42, 44 are located opposite the three power terminals 32, 34,36. The signal terminals 42, 44 each extend across inside and outsidethe encapsulant 50. The first signal terminals 42 are parallel to oneanother and project from the encapsulant 50 along the first direction(the up-down direction in FIGS. 1 and 2). Each of the first signalterminals 42 is connected to corresponding one of the signal pads 12 cof the first semiconductor element 12 within the encapsulant 50. Theplurality of first signal terminals 42 includes, for example, a gatesignal terminal connected to a gate of the IGBT of the firstsemiconductor element 12 (see FIG. 4). In the present embodiment, thefirst signal terminals 42 and the signal pads 12 c are connected viabonding wires 46. As another embodiment, the first signal terminals 42and the signal pads 12 c may be directly connected by, for example,soldering, brazing, or the like.

Similarly, the second signal terminals 44 are parallel to one anotherand project from the encapsulant 50 along the first direction. Each ofthe second signal terminals 44 is connected to corresponding one of thesignal pads 14 c of the second semiconductor element 14 within theencapsulant 50. The plurality of second signal terminals 44 includes,for example, a gate signal terminal connected to a gate of the IGBT ofthe second semiconductor element 14. In the present embodiment, thesecond signal terminals 44 and the signal pads 14 c are connected viabonding wires 48. As another embodiment, the second signal terminals 44and the signal pads 14 c may be directly connected by, for example,soldering, brazing, or the like.

According to the above configuration, in the semiconductor device 10 ofthe present embodiment, the first power terminal 32 and the second powerterminal 34 are connected via the first semiconductor element 12, andthe second power terminal 34 and the third power terminal 36 areconnected via the second semiconductor element 14. Providing agate-drive signal via one of the first signal terminals 42 can turn onand off the IGBT of the first semiconductor element 12. Moreover,providing a gate-drive signal via one of the second signal terminals 44can turn on and off the IGBT of the second semiconductor element 14. Thesemiconductor device 10 in the present embodiment has such aconfiguration, and thus can configure a pair of upper and lower arms ina power conversion circuit such as a converter and an inverter.

In the semiconductor device 10 in the present embodiment, the firstpower terminal 32 is connected to the first conductor plate 22. In sucha configuration, heat of the first power terminal 32 could transfer tothe first semiconductor element 12 via the first conductor plate 22. Forexample, the first power terminal 32 may generate heat since it allows arelatively large current to flow therein. Moreover, the first powerterminal 32 is often welded to an external circuit member (e.g., a busbar), and tends to generate relatively large amount of heat at itswelded site. If such heat transfers to the first semiconductor element12, a temperature of the first semiconductor element 12 is therebyrisen, which may create a need to restrict an operation of the firstsemiconductor element 12.

In this regard, in the semiconductor device 10 in the presentembodiment, the first semiconductor element 12 is offset relative to acenter of the first conductor plate 22, to be apart from the first powerterminal 32. Specifically, as shown in FIG. 5, the main surface 23 ofthe first conductor plate 22 has a generally rectangular shape, andincludes a first side 23 a located close to the first power terminal 32and a second side 23 b located opposite the first side 23 a with respectto the first direction. With respect to the first direction, a distanceD1 from the first semiconductor element 12 to the first side 23 a islarger than a distance D2 from the first semiconductor element 12 to thesecond side 23 b. As described above, the first direction is a directionin which the first power terminal 32 projects from the encapsulant 50,and refers to the up-down direction in FIG. 5. As such, disposing thefirst semiconductor element 12 relatively apart from the first powerterminal 32 can suppress transfer of the heat of the first powerterminal 32 to the first semiconductor element 12 via the firstconductor plate 22.

Particularly, in the semiconductor device 10 in the present embodiment,the distance D1 from the first semiconductor element 12 to the firstside 23 a is equal to or larger than a half of a size S1 of the firstsemiconductor element 12 with respect to the first direction. As such,the distance D1 from the first semiconductor element 12 to the firstside 23 a (which is approximately a distance from the firstsemiconductor element 12 to the first power terminal 32) is sufficientlylarger than that in conventional semiconductor devices. This caneffectively suppress transfer of the heat of the first power terminal 32to the first semiconductor element 12 via the first conductor plate 22.

Additionally, in the semiconductor device 10 in the present embodiment,with respect to the first direction, the distance D1 from the firstsemiconductor element 12 to the first side 23 a is at least twice thedistance D2 from the first semiconductor element 12 to the second side23 b. The first semiconductor element 12 is thereby sufficiently offsetrelative to the center of the first conductor plate 22. This caneffectively suppress transfer of the heat of the first power terminal 32to the first semiconductor element 12 via the first conductor plate 22.

As described above, the semiconductor device 10 in the presentembodiment further includes the second conductor plate 24. The secondconductor plate 24 is opposed to the first conductor plate 22 with thefirst semiconductor element 12 interposed therebetween, and includes themain surface 25 connected to the first semiconductor element 12 withinthe encapsulant 50. Since the second conductor plate 24 is adjacent tothe first power terminal 32, it could transfer the heat of the firstpower terminal 32 to the first semiconductor element 12. In view ofthis, the first semiconductor element 12 is also offset relative to acenter of the second conductor plate 24, to be apart from the firstpower terminal 32.

Specifically, as shown in FIG. 6, the main surface 25 of the secondconductor plate 24 has a generally rectangular shape, and includes afirst side 25 a located close to the first power terminal 32 and asecond side 25 b located opposite the first side 25 a with respect tothe first direction. With respect to the first direction, a distance D5from the first semiconductor element 12 to the first side 25 a of thesecond conductor plate 24 is larger than a distance D6 from the firstsemiconductor element 12 to the second side 25 b of the second conductorplate 24. This can suppress transfer of the heat of the first powerterminal 32 to the first semiconductor element 12 via the encapsulant 50and the second conductor plate 24 (especially via the second conductorplate 24).

In the second conductor plate 24 as well, the distance D5 from the firstsemiconductor element 12 to the first side 25 a is equal to or largerthan the half of the size S1 of the first semiconductor element 12 withrespect to the first direction. Additionally, with respect to the firstdirection, the distance D5 from the first semiconductor element 12 tothe first side 25 a is at least twice the distance D6 from the firstsemiconductor element 12 to the second side 25 b. These configurationscan effectively suppress transfer of the heat of the first powerterminal 32 to the first semiconductor element 12 via the encapsulant 50and the second conductor plate 24.

As described above, the semiconductor device 10 in the presentembodiment further includes the third conductor plate 26. The thirdconductor plate 26 is located side by side with the first conductorplate 22 in a second direction perpendicular to the first direction. Thethird conductor plate 26 has the second power terminal 34 connectedthereto, and the second power terminal 34 extends from the encapsulant50 along the first direction. In such a structure, heat of the secondpower terminal 34 could transfer to the second semiconductor element 14via the third conductor plate 26. In view of this, the secondsemiconductor element 14 is also offset relative to a center of thethird conductor plate 26, to be apart from the second power terminal 34.

Specifically, as shown in FIG. 5, the main surface 27 of the thirdconductor plate 26 has a generally rectangular shape, and includes afirst side 27 a located close to the second power terminal 34 and asecond side 27 b located opposite the first side 27 a with respect tothe first direction. With respect to the first direction, a distance D3from the second semiconductor element 14 to the first side 27 a of thethird conductor plate 26 is larger than a distance D4 from the secondsemiconductor element 14 to the second side 27 b of the third conductorplate 26. Such a configuration can suppress transfer of the heat of thesecond power terminal 34 to the second semiconductor element 14 via thethird conductor plate 26.

In the third conductor plate 26 as well, the distance D3 from the secondsemiconductor element 14 to the first side 27 a is equal to or largerthan a half of a size S2 of the second semiconductor element 14 withrespect to the first direction. Additionally, with respect to the firstdirection, the distance D3 from the second semiconductor element 14 tothe first side 27 a is at least twice the distance D4 from the secondsemiconductor element 14 to the second side 27 b. These configurationscan effectively suppress transfer of the heat of the second powerterminal 34 to the second semiconductor element 14 via the thirdconductor plate 26.

As described above, the semiconductor device 10 in the presentembodiment further includes the fourth conductor plate 28. The fourthconductor plate 28 is opposed to the third conductor plate 26 with thesecond semiconductor element 14 interposed therebetween, and includesthe main surface 29 connected to the second semiconductor element 14within the encapsulant 50. Since the fourth conductor plate 28 isadjacent to the second power terminal 34, it could transfer the heat ofthe second power terminal 34 to the second semiconductor element 14.Moreover, since the fourth conductor plate 28 is connected to the thirdpower terminal 36, it could also transfer heat of the third powerterminal 36 to the second semiconductor element 14. In view of this, thesecond semiconductor element 14 is also offset relative to a center ofthe fourth conductor plate 28, to be apart from the second powerterminal 34 and the third power terminal 36.

Specifically, as shown in FIG. 6, the main surface 29 of the fourthconductor plate 28 has a generally rectangular shape, and includes afirst side 29 a located close to the second power terminal 34 and asecond side 29 b located opposite the first side 29 a with respect tothe first direction. With respect to the first direction, a distance D7from the second semiconductor element 14 to the first side 29 a of thefourth conductor plate 28 is larger than a distance D8 from the secondsemiconductor element 14 to the second side 29 b of the fourth conductorplate 28. This can suppress transfer of the heat of the second powerterminal 34 and the third power terminal 36 to the second semiconductorelement 14 via the fourth conductor plate 28.

In the fourth conductor plate 28 as well, the distance D7 from thesecond semiconductor element 14 to the first side 29 a is equal to orlarger than the half of the size S2 of the second semiconductor element14 with respect to the first direction. Additionally, with respect tothe first direction, the distance D7 from the second semiconductorelement 14 to the first side 29 a is at least twice the distance D8 fromthe second semiconductor element 14 to the second side 29 b. Theseconfigurations can effectively suppress transfer of the heat of thesecond power terminal 34 and the third power terminal 36 to the secondsemiconductor element 14 via the fourth conductor plate 28.

In the semiconductor device 10 in the present embodiment, the thirdconductor plate 26 is connected to the second conductor plate 24 via thefirst connector portion 38 located between the second conductor plate 24and the third conductor plate 26. Although not particularly limited, thefirst connector portion 38 may be near the first semiconductor element12 and the second semiconductor element 14, which shortens paths ofcurrent that flows in the semiconductor device 10. Specifically, asshown in FIG. 7, in a plan view along a direction perpendicular to thethird conductor plate 26, at least a half of the first semiconductorelement 12 and at least a half of the second semiconductor element 14may each be located within a region R1 that is defined by virtuallyexpanding the first connector portion 38 in the second direction. Such aconfiguration allows the first connector portion 38 to be disposedsufficiently near the first semiconductor element 12 and the secondsemiconductor element 14. This shortens a current path between the firstsemiconductor element 12 and the first connector portion 38, and acurrent path between the second semiconductor element 14 and the firstconnector portion 38, so electrical loss in these paths can be reduced.

In the semiconductor device 10 in the present embodiment, the thirdpower terminal 36 is connected to the fourth conductor plate 28 via thesecond connector portion 40. Although not particularly limited, thesecond connector portion 40 may be far from the first semiconductorelement 12 and the second semiconductor element 14, by which transfer ofthe heat of the third power terminal 36 to the first semiconductorelement 12 and the second semiconductor element 14 can be suppressed.Specifically, as shown in FIG. 7, in a plan view along a directionperpendicular to the fourth conductor plate 28, neither the firstsemiconductor element 12 nor the second semiconductor element 14 may belocated within a region R2 that is defined by virtually expanding thesecond connector portion 40 in the second direction. Such aconfiguration allows the first semiconductor element 12 and the secondsemiconductor element 14 to be located far from the second connectorportion 40 and the third power terminal 36, and hence can suppresstransfer of the heat of the third power terminal 36 to the firstsemiconductor element 12 and the second semiconductor element 14.

Next, a method of manufacturing the semiconductor device 10 will bedescribed. It should be noted that the following description does notlimit the method of manufacturing the semiconductor device 10. As shownin FIG. 8, in the method of manufacturing the semiconductor device 10, asemi-finished product 10 a of the semiconductor device 10 is set into acavity 102 of a mold 100. Next, a molten encapsulating material 50 a(e.g., an insulating material such as an epoxy resin) is poured into thecavity 102 to mold the encapsulant 50. Here, a configuration of thesemi-finished product 10 a is equivalent to the configuration of thesemiconductor device 10 with the encapsulant 50 removed. It should benoted that one or more of the power terminals 32, 34, 36 and the signalterminals 42, 44 may be integrated in a lead frame.

The mold 100 is provided with a gate 104, from which the encapsulatingmaterial 50 a flows into the cavity 102. The encapsulating material 50 athat have flowed into the cavity 102 proceeds between the firstconductor plate 22 and the second conductor plate 24, and between thethird conductor plate 26 and the fourth conductor plate 28. Between thefirst conductor plate 22 and the second conductor plate 24, theencapsulating material 50 a is divided to flow on both sides of thefirst semiconductor element 12, and merges again at a position beyondthe first semiconductor element 12. At this time, at the position wherethe encapsulating material 50 a merged, there may be a case where air 52is confined between the encapsulating material 50 a and the firstsemiconductor element 12. If such air 52 remains in the encapsulant 50in the finished semiconductor device 10, this could affect, for example,durability of the semiconductor device 10. Especially if the air 52 islocated between the first semiconductor element 12 and the encapsulant50 (i.e., the air 52 is in contact with the first semiconductor element12), the semiconductor device 10 would be affected in a greater degree.

As described above, in the semiconductor device 10 in the presentembodiment, the first semiconductor element 12 is not located at thecenter of the first conductor plate 22 or at the center of the secondconductor plate 24, but is offset from these centers. In this regard,the same applies to the semi-finished product 10 a. The firstsemiconductor element 12 is relatively near the gate 104 of the mold100, so the above-described confinement of the air 52 occurs at arelatively early stage. Therefore, after the confinement of the air 52occurs, the encapsulating material 50 a continues to be poured for arelatively long period of time. Consequently, as shown in FIG. 9, theconfined air 52 moves away from the first semiconductor element 12 alongwith the flow of the encapsulating material 50 a. As such, even if theair 52 is confined in the encapsulating material 50 a, the air 52 (i.e.,a bubble) is located apart from the first semiconductor element 12 inthe finished semiconductor device 10. Accordingly, even if the air 52remains in the encapsulant 50, it would affect the semiconductor device10 in a less degree. The same applies to a space between the thirdconductor plate 26 and the fourth conductor plate 28, and air that isconfined by the encapsulating material 50 a is suppressed from remainingin contact with the second semiconductor element 14.

What is claimed is:
 1. A semiconductor device comprising: a firstconductor plate; a first semiconductor element that is a solesemiconductor element disposed on a main surface of the first conductorplate; an encapsulant encapsulating the first semiconductor element; anda first power terminal connected to the first conductor plate within theencapsulant and projecting from the encapsulant along a first direction,wherein the main surface of the first conductor plate comprises a firstside located close to the first power terminal and a second side locatedopposite the first side with respect to the first direction, and withrespect to the first direction, a distance from the first semiconductorelement to the first side is larger than a distance from the firstsemiconductor element to the second side.
 2. The semiconductor deviceaccording to claim 1, wherein the distance from the first semiconductorelement to the first side is equal to or larger than a half of a size ofthe first semiconductor element with respect to the first direction. 3.The semiconductor device according to claim 1, wherein with respect tothe first direction, the distance from the first semiconductor elementto the first side is at least twice the distance from the firstsemiconductor element to the second side.
 4. The semiconductor deviceaccording to claim 1, further comprising a second conductor plateopposed to the first conductor plate with the first semiconductorelement interposed therebetween, wherein the second conductor platecomprises a main surface connected to the first semiconductor elementwithin the encapsulant.
 5. The semiconductor device according to claim4, wherein the main surface of the second conductor plate comprises afirst side located close to the first power terminal and a second sidelocated opposite the first side with respect to the first direction, andwith respect to the first direction, a distance from the firstsemiconductor element to the first side of the second conductor plate islarger than a distance from the first semiconductor element to thesecond side of the second conductor plate.
 6. The semiconductor deviceaccording to claim 4, further comprising: a third conductor platelocated side by side with the first conductor plate in a seconddirection perpendicular to the first direction; a second semiconductorelement that is a sole semiconductor element disposed on a main surfaceof the third conductor plate within the encapsulant; and a second powerterminal connected to the third conductor plate within the encapsulantand projecting from the encapsulant along the first direction, whereinthe main surface of the third conductor plate comprises a first sidelocated close to the second power terminal and a second side locatedopposite the first side with respect to the first direction, and withrespect to the first direction, a distance from the second semiconductorelement to the first side of the third conductor plate is larger than adistance from the second semiconductor element to the second side of thethird conductor plate.
 7. The semiconductor device according to claim 6,wherein the third conductor plate is connected to the second conductorplate via a first connector portion located between the second conductorplate and the third conductor plate, and in a plan view along adirection perpendicular to the third conductor plate, at least a half ofthe first semiconductor element and at least a half of the secondsemiconductor element are each located within a region defined byvirtually expanding the first connector portion in the second direction.8. The semiconductor device according to claim 7, further comprising: afourth conductor plate opposed to the third conductor plate with thesecond semiconductor element interposed therebetween; and a third powerterminal connected to the fourth conductor plate within the encapsulantand projecting from the encapsulant along the first direction, whereinthe fourth conductor plate is located side by side with the secondconductor plate in the second direction and is connected to the thirdpower terminal via a second connector portion, and in a plan view alonga direction perpendicular to the fourth conductor plate, the secondconnector portion is located between the second conductor plate and thefourth conductor plate and is further located between the third powerterminal and the first connector portion.
 9. The semiconductor deviceaccording to claim 8, wherein in the plan view along the directionperpendicular to the fourth conductor plate, neither the firstsemiconductor element nor the second semiconductor element is locatedwithin a region defined by virtually expanding the second connectorportion in the second direction.